get_some_context returns gpu devices first, then cpu devices if no gpu's available
get_some_context returns gpu devices first, then cpu devices if no gpu's available

JuliaPackageMirrors/OpenCL.jl,yuyichao/OpenCL.jl,JuliaPackageMirrors/OpenCL.jl,tkelman/OpenCL.jl,yuyichao/OpenCL.jl,tkelman/OpenCL.jl